Light or solar energy harvesting is needed for autonomous wireless transceivers which are compact in size, have a low cost, are light weight, and may be mobile. Moreover, portable, wearable, or other wireless devices may have non-linear shapes and may be flexible. Antennas other than wires are generally manufactured on a rigid or flexible printed circuit board or material, using a metalized surface or metalized strip lines.
The antenna is a distinct electronic element which has to interface to the RF front-end circuits. Some wireless systems use smart antenna technology, such as MIMO (multiple-input multiple-output), where antenna diversity is achieved by using two or more antennas for higher spectral efficiency and link reliability, which adds to the cost and size. Software-defined-radios (SDR) and ultra-wideband (UWB) transceivers use a wide frequency bandwidth requiring large bandwidth antennas. Other transceivers combine multiple standards into one device, e.g., GPS at 1.5 GHz, GSM at 900 MHz and 1.8 GHz, UMTS at 2100 MHz, and LTE in the 2600 MHz band in Europe. Antenna arrays also use multiple antenna elements for the purpose of achieving higher antenna gain and directivity. Antenna arrays are commonly used in space and terrestrial communications.
Nowadays, the antenna and packaging of the wireless system have become the bottleneck of the system by increasing to one-third of the cost of the wireless module, far surpassing the cost of the electronic integrated circuits. Energy efficient designs are needed to minimize the d.c. (DC) power consumption by integrating all electronic devices together and minimizing the number of elements, leading to smart system integration, such as system-in-package, system-on-chip, system-on-package, and lab-on-a-chip.
Nowadays, antenna elements are either bought as a separate device or are part of a circuit board where they interface with other electronic devices, or within the casing of enclosed electronic devices. The dual functionality of a photovoltaic cell for absorbing light energy and radiating and/or receiving electromagnetic waves has been initially investigated for satellite and terrestrial communication applications. Unfortunately, prior art photovoltaic cell, or “solar antenna”, and radio-frequency antennas solutions presented do not offer the flexibility and the compactness required for low-power transceiver systems, such as for autonomous wireless sensor networks, which is a drawback.
In addition, these prior art photovoltaic cell and radio-frequency antennas are not easily integrated with other electronic devices and are thus bulky.
Research experiments have been conducted by M. Tanaka, Y. Suzuki, K. Araki, and R. Suzuki for combining a photovoltaic cell and a radio-frequency antenna into a single device and have been published in “Microstrip antenna with solar cells for microsatellites”, Electronic Letters, vol. 31, no. 1, pp. 5-6, Jan. 5, 1995. Unfortunately, the prior art photovoltaic cell and radio-frequency antennas disclosed are primarily aimed at satellite and terrestrial applications which are restricted to narrowband frequency operation which is a drawback.
Common patch antenna elements have been disclosed by Bendel et al. in U.S. Pat. No. 6,395,971. These elements interface to other electronic devices, such as an RF transceiver via a shielded cable, one example of such embodiment has been disclosed by Kiefer in U.S. Pat. No. 6,590,150. Unfortunately, in such embodiment, power losses are added to the transmitting or received signals, which decreases the energy efficiency of the wireless system which is also a drawback.
Previously published materials have shown many drawbacks that render them cumbersome for compact autonomous wireless smart integrated systems.
Moreover and in the case where the antenna is a patch antenna, an RF ground plane is required. The RF ground plane is located on an insulating material substrate, below the photovoltaic cell and radio-frequency antenna. A patch antenna may not be used for ultra-wideband (>20% or >500 MHz) frequency bandwidths. As the front contacts of the photovoltaic cell are located on its top surface for providing an electrical potential, a top to down interconnection to a substrate is required.
There is a need for an assembly that will overcome at least one of the above-identified drawbacks.
Features of the invention will be apparent from review of the disclosure, drawings, and description of the invention below.